Test writing method and information recording device

ABSTRACT

The object of the present invention is to provide a test writing method for seeking the optimum write power correctly and in a short time under a high speed recording condition in a test writing method and an information recording device for recording information by forming different marks from the unrecorded part by injecting energy onto the recording medium. To achieve the above object, even number length marks and odd number length marks are separately test written in the 2T strategy to seek the respective optimum write power. Due to the possibility of enhancing the precision of test writing, a good recording ability can be obtained.

CLAIM OF PRIORITY

The present application claims priority from Japanese application JP2005-033771 filed on Feb. 10, 2005, the content of which is herebyincorporated by reference into this application.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to U.S. application Ser. No. 10/931040 filedon Sep. 1, 2004, the disclosure of which is hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to a test writing method and aninformation recording device for recording information by forming marksdifferent from unrecorded portion by applying energy into a recordingmedium.

BACKGROUND OF THE INVENTION

Test writing has been undertaken in order to record information with ahigh precision on optical disks. Test writing means actions for seekingthe optimum recording parameters in response to the environmentaltemperature at that time and the characteristics of laser beamtransmitted by the drives loaded in order to form good recording marks.Optical disks such as DVD-RW, DVD+RV, BD-RE and the like use materialsof a composition called “eutectic system” in their recording film. Inthe recording devices now being produced, normally for test writing onthese optical disks, the recording conditions prewritten in the opticaldisk are read in the first place, and then the laser power is adjusted.The recording condition referred here, for example, the set value oflaser power indicated by the write power level (Pw) of a high laserpower, the erasing power level (Pe) of a middle power, a set value oflaser power represented by the bias power level (Pb), and the respectivepulse width of the first pulse constituting multi pulse wave, aplurality of successive middle pulse and last pulse.

In actual test writing, the method of fixing the ratio between the Pwand the Pe prewritten in the optical disk based on these recordingconditions and finding out the optimum recording conditions of the laserpower as parameters has been adopted. This method is called “the optimumpower control method (OPC).” In relatively low speed recording such asBD1×, DVD-RW2-4× and the like, good recording quality has been obtainedby test writing by changing only laser power of such a fixed Pw/Peratio.

The research and development efforts are now being made in thehigh-speed recording and reproduction technology in these optical disks.For example, in Optical Data Storage 2003 and Proceedings of SPIE Vol.5069 (2003), p 130 (Non-patent Document 1), a recording technology witha recording speed of 216 Mbps corresponding to BD 6× is described. Asthe recording speed accelerates, write strategy adapted to higher speed,or so-called 2T strategy is now being studied. 2T strategy means a writestrategy that equalizes the number of recording pulses of a pair ofneighboring marks, one of even number length and the other of odd numberlength. Specifically, as FIG. 2 shows, for example when the shortestmark length is a 2T mark, the 2T mark and the 3T mark emits a singlerectangular pulse, and the 4T mark and the 5T mark emits two pulses, thefirst pulse and the last pulse. The 6T mark and the 7T mark emit threepulses, a first pulse, a middle pulse and a last pulse.

As an example of this 2T strategy, the Japanese Patent Application LaidOpen 1997-134525 (corresponding U.S. Pat. No. 5,732,062, PatentDocument 1) describes that, for recording either a mark length from evennumber length mark or odd number length mark corresponding to therecording channel clock frequency in the multi pulse recording systemconsisting of the first pulse, a plurality of successive middle pulsesand the last pulse, the pulse width of the first pulse and the lastpulse is made almost identical with the recording channel clockfrequency.

And the Japanese Patent Application Laid Open 1999-175976 (correspondingto U.S. Pat. No. 6,256,277, Patent Document 277) proposes the method offorming a recording wavelength in such a way that the shortest pulsewidth among the multi pulse may be longer than a half of the windowwidth. This will enable to secure a sufficient cooling time of therecording medium, to reduce the frequency component of the laser drivingcurrent and therefore to form marks with a sufficient accuracy during ahigh-speed transmission.

Furthermore, the Japanese Patent Application Laid Open 2003-30833(Patent Document 3) as well as the Japanese Patent Application1999-175976 adopt the method of not only making the frequency of themiddle pulse string longer than the recording channel clock frequencybut also of changing the edge position of the first pulse and the lastpulse depending on the preceding space or the succeeding space. It isstated that the present method enables to restrict to the minimum extentpossible edge shift due to heat interference in the track directioninvolved in the case of recording at a high density and hightransmission rate and therefore to control recording at a highprecision.

And Japanese Patent Application Laid Open 2001-331936 (corresponding toUS 2001/053115A1, Patent Document 4) describes the formation of pulsestring by shifting the reference clock depending on the even code trainor the odd code train and the formation of the write pulse strategy foreven number and odd number by changing the duty ratio for the firstpulse and the last pulse respectively in the case of odd number and thecase of even number.

Incidentally, with regard to the recording mark shape control effect ofthe 2T strategy during the high-transmission rate recording is describedin details, for example, in Optical Data Storage 2000, and Proceedingsof SPIE Vol. 4090 (2000), p 135 (Non-Patent Document 2).

-   [Patent Document 1] Japanese Patent Application Laid Open    1997-134525-   [Patent Document 2] Japanese Patent Application Laid Open    1999-175976-   [Patent Document 3] Japanese Patent Application Laid Open 2003-30833-   [Patent Document 4] Japanese Patent Application Laid Open    2001-331936-   [Non-Patent Document 1] Optical Data Storage 2003, Proceedings of    SPIE Vol. 5069 (2003), p 130-   [Non-Patent Document 2] Optical Data Storage 2000, Proceedings of    SPIE Vol. 4090 (2000), p 135

SUMMARY OF THE INVENTION

According to the prior test writing method described above or so-calledOPC, laser power based on the fixed ratio of Pw/Pe is optimized, and therecording condition for the best quality has been sought thereby.However, according to the examination of the inventors, it has beennewly found very difficult to obtain sufficiently good mark qualityaccording to the OPC method using laser power with fixed ratio of Pw/Peas parameter when attempts are made to achieve a recording speed inexcess of BD 4×, or DVD±RW 8×. This is due to the following reason. Incase of a low speed recording such as BD1× or DVD±RW 2.4×, because of asufficient time between the irradiation of the first pulse and the nextpulse (the middle pulse or the last pulse), the recording film issufficiently cooled at the time of irradiation of the next pulse. In thecase of a high-speed, on the other hand, because of a reduction of timebetween the irradiation of the first pulse and that of the next pulse,the cooling speed of the recording film becomes relatively insufficient,and therefore the problem of insufficient cooling of the front edgeportion formed by the first pulse develops. When the next pulse isirradiated while the front edge part is not sufficiently cooled, thefront edge part crystallizes leading to the development of an edgefluctuation or an edge shift. This is equal to a deterioration ofrecording quality due to an acceleration of the recording time.

As the recording speed rises, variation in the characteristics of laserdevices mounted on drives available on the market cannot be ignored. Forexample, the writing channel clock frequency T at BD 4× will beapproximately 3.8 ns, making it necessary to control the laser strategyto 1 ns or less. However, since the present rising time and falling timeof laser are approximately 1-2 ns, the strategy control of 1 sn is closeto the physical limit, and the individual difference in rising andfalling of laser will have important impacts on the shape of recordingmarks. Furthermore, in the case where the waveform of luminescencediffers between drives due to the variation of spot diameter betweendrives and the like, the problem such as that of individual differencesbetween devices absorbed by the medium at low speed looming up at highspeed has developed.

Therefore, the present invention takes the following structure.

(1) The write patterns classified according to the excess obtained bydividing mark lengths in the recording code train by an integer constantof n=2 or more corresponding to the mark length of a natural number nxin the window width are respectively recorded and reproduced, and awrite power P0 at which modulation gets 0 from the relationship betweenthe modulation and the write power is calculated, and a value obtainedby multiplying P0 by a certain constant p is set as the write power ofeach write pattern.

As this process enables to adjust the write power for each write patternclassified by the excess, write performance improves better than thecase wherein the write power of a plurality of write patterns are setacross the board in the same way, and the write margin can be expanded.

In other words, in the case of 2T strategy, the process will be asfollows. An even number length writing pattern consisting of a length ofrecording marks corresponding to an even number times of the referenceclock frequency and an odd number length writing pattern consisting ofrecording marks of a length corresponding to an odd number times arerecorded and reproduced by changing their respective write power, andbased on the results of reproduction thereof, the optimum write power ofthe even number length and the optimum write power of the odd numberlength are set. In other words, in case of forming a write strategy fortest writing by using a recording laser beam consisting of L pulses bytaking the time length of a recording mark as nT (T is the referenceclock frequency and n is a natural number of 2 or more), the writepattern will be (1) an even number length pattern formed by marks ofnT=2LT, in other words, recording marks formed by a length correspondingto a even number times of the reference clock frequency, and (2) an oddnumber length write pattern composed of marks of nT=(2L+1) T, in otherwords recording marks of a length corresponding to an odd number times,and (1) the even number length write pattern and (2) the odd numberlength write pattern will be respectively recorded. And these writepatterns are reproduced, and the relationship of modulation calculatedfrom the write power and reproduced signals is calculated respectivelyfor the even number length and the odd number length, and the valueobtained by multiplying the power P0 at which modulation gets 0 by acertain constant p serves as the basis of setting the write power foreach write pattern.

Then, in the case of 3T strategy, the process will be as follows. In thecase of nT=3LT system, (1) a write pattern formed by the nT=3LT mark,(2) a write pattern formed by the nT=(3L−2) T, and (3) a write patternformed by the nT=(3L−1) T mark are used to record these, and therelationship of modulation is calculated from the write power and thereproduced signals, and the write power is set based on the P0 obtainedfrom each write pattern.

And, in the case of 4T strategy, the process will be as follows. In thecase of nT=4LT, (1) a write pattern formed by the nT=4LT, (2) a writepattern formed by the nT=(4L−2) T mark, (3) a write pattern formed bythe nT=(4L−1) T mark, and (4) a write pattern formed by the nT=(4L+1) Tmark are used, these are recorded respectively, the relationship ofmodulation is calculated from the write power and the reproducedsignals, and the write power is set based on the P0 obtained from eachwrite pattern.

(2) And it is preferable to conduct test writing by using a confirmationpattern and the write power set by each write pattern described above,and to readjust the write power of each write pattern. This processenables to fine adjust the write power and to obtain the optimumrecording condition.

(3) The constant p for multiplying the write power P0 so that themodulation may get 0 is preferably within a range between 1.5 and 3.0.If it is smaller than 1.5, it will be difficult to obtain a sufficientamplitude, and when it is larger than 3.0. the mark width is too largeand causes the adjacent mark to crystallize or cross erase. It is morepreferable to choose a value between 2.0 and 2.8 for p. The choice of avalue of 2.0 or higher for p is more preferable because it enables toreduce any growth in jitter due to variations in power at the time oftest writing resulting from a write power offset and other recordingconditions. And the choice of a value of 2.8 or less for p is morepreferable because it enables to prevent irradiation due to over powerand to prevent any fall in performance due to multiple rewriting.

(4) Among a plurality of write patterns classified by the excessobtained by dividing a mark length in the recording code traincorresponding to the mark length of n natural number in the window widthby an integer constant of n=2 or more, the pattern A is chosen, recordedand reproduced by changing the write power, a write power P0 (A) atwhich modulation is reduced to 0 from the relationship between themodulation and the write power is calculated, a value obtained bymultiplying P0 (A) by a certain constant p is set as the write power Pw(A) of each write pattern, and the write powers of other write patternsare set so that they may be almost the same as the modulation mod (A) atPw (A).

In this way, the write power will be set for each write patternclassified according to the excess, and almost the same modulation canbe obtained even if the write pattern may be different. Therefore, therecording ability improves better than the case wherein all the writepowers of a plurality of write patterns are set in the same way acrossthe board, and the recording margin can be expanded. Also, because it isno longer necessary to calculate a write power P0 (A) at whichmodulation gets 0 for each of a plurality of write patterns, the testwriting time can be shortened.

For example, an example in the case of 2T strategy will be shown below.An odd number length write pattern consisting of recording marks of alength corresponding to an odd number times of the reference clockfrequency is used, recorded and reproduced by changing the write powerto calculate the write power P0 (odd) at which modulation gets 0 fromthe relationship between the modulation and the write power, and thevalue obtained by multiplying the P0 (odd) by a certain constant p isset as the write power Pw (odd) for the write pattern. A write power foran even number length write pattern that will be almost the same valueas the modulation mod (odd) by the Pw (odd) is calculated, and this willbe the write power Pw (even) for the even number length write pattern.Here again, the write power of the Pw (odd) and the Pw (even) may beused to undertake test writings by a confirmation pattern and readjustthe write power of each write pattern. At this time, it will beeffective to fine adjust only the Pw (even) by pegging the Pw (odd).Such test writings by means of a confirmation pattern will enable tofine adjust the write power and to obtain the optimum recordingconditions.

In addition, after the optimum write power (odd) has been obtained by anodd number length mark, it is possible to obtain Pw (even) bymultiplying Pw (odd) by a certain constant q or by adding a constant ras a means for obtaining the optimum write power (even) for a writepattern consisting of only an even number length of marks.

In the case of 2T strategy, a write pattern consisting of an even numberlength mark or a write pattern consisting of an odd number length istest written to obtain a write power, and the write power is multipliedby a constant q or a constant r is added thereto to obtain the writepower of the other write pattern. In other words, the relationshipbetween the write power Pw (odd) for recording the write patternconsisting of an odd number length and the write power Pw (even) forrecording the write pattern consisting of an even number length is Pw(odd)=q×Pw (even) or Pw (odd)=Pw (even)+r. In the 2T strategy, a pair ofadjacent even number length mark and odd number length mark are recordedby using a write strategy consisting of a same number of pulses. Forexample, if the shortest mark length is 2T mark, 2T mark and 3T markgenerate a single rectangular pulse, and 4T mark and 5T mark generatetwo pulses consisting of the first pulse and the last pulse. At thistime, an even number length mark and an odd number length mark may havea different recording sensibility due to the influence of write strategyform and the thermal property and crystallization property of themedium. When the relationship between the write power Pw (odd) forrecording a write pattern consisting of an odd number length and thewrite power Pw (even) for recording a write pattern consisting of aneven number length is correlated by a mathematical formula, it is enoughto test write only one of the write patterns, and therefore the timerequired for test writing can be curtailed. The value of the constant qand the constant r should preferably be set before shipping the drive.Or, when a medium is first loaded, the value of q and r may bedetermined by learning and the medium ID and the value of q and r may becorrelated.

(6) The asymmetry of the shortest mark length among write patternsincluding the odd number minimum length mark and the asymmetry of theshortest mark length among write patterns including the even numberminimum length mark are calculated and the write power Pw (odd) forrecording the write patterns consisting of an odd number length and thewrite power Pw (even) for recording the write patterns consisting of aneven number length are respectively set in such a way that both of theformer may be nearly identical. For example, in the case where theminimum mark is a 3T mark, the respective power by which the asymmetryof 3T mark Asym (3T) among the write patterns including 3T marks and theasymmetry of 4T mark Asym (4T) among the write patterns including 4Tmarks are nearly identical is taken as the write power. At this time,only the asymmetry of 3T marks Asym (3T) may be reproduced for the writepatterns of an odd number length and the asymmetry of 4T marks Asym (4T)may be reproduced for the even number length marks.

As the setting of write powers by taking into account such asymmetryconcerns values obtained by comparing different mark lengths recorded atthe same time, even if a power offset due to defocusing, an electricoffset or the like occurs during a test writing, the impacts of theseoffsets can be controlled. On the other hand, signal amplitude,modulation and the like are directly affected by these offsets, theyrequire attention during test writing for setting write power. Here, theterm asymmetry has been used for the sake of consistency. Actually,however, it is better to use β. The β is defined by the followingformula, and is governed by the technical standard of DVD-RW and thelike.β=(A1+A2)/(A1−A2)wherein β is a value calculated from AC coupled HF signals, and A1 andA2 represent respectively the peak levels (the high level and the lowlevel) of AC coupled HF signals. In other words, (A1+A2) represents thedifference between the peak levels, and (A1−A2) represents thepeak-to-peak values of the HF signals.

And the write power may be set by using γ. The γ is defined by thefollowing formula and is governed, like β, by the technical standard ofDVD-RW and the like.γ=(dm/dPw)*(Pw/m)wherein m represents the modulation of the HF signals.

Such a method is effective not only in optical disks of the type havinga recording layer but is particularly effective in optical disks of thetype having multiple recording layers. For example, an optical diskhaving double recording layers is disturbed with the problem of therecording margin for each recording layer getting narrower than that ofa disk having a single recording layer. However, as in the presentinvention, it becomes possible to expand the recording margin bycontrolling the write power according to the write pattern. This isparticularly effective for test writing on rewritable media using aeutectic type recording film such as DVD-RW, DVD+RW, BD-RE and the like.

The conduct of such test writings sometimes requires more time than thatof a similar test writing-in the past. However, in the case of a mediumrequiring the operation of “printing” (writing) data such as DVD+RW,BD-RE and the like, the time required for test writing a few seconds,and because of an overwhelmingly longer time required for “printing”(writing) operation (for example 10 minutes), even if the time requiredfor test writing exceeds five times, the time of keeping the userwaiting barely changes, and the convenience of the optical disk does notdecrease nor does it constitute a demerit for the user.

In addition, the present invention is particularly effective forhigh-speed recording and is particularly effective for recording on arecording type medium using a so-called eutectic type and crystal growthtype recording film with a condition of a recording speed of 20 m/s ormore.

And a modulation of 0 indicates that absolutely no mark has been formed.Therefore, if the write power is so low that the recording film may beunable to reach a melting temperature, the modulation gets 0, and in thepresent invention the maximum write power effectively making themodulation 0 is important. For obtaining a modulation of 0 on a drive,the modulation in effect at the time of changing the write power may berespectively obtained and the relationship between the write power andthe modulation may be calculated based on the specified formula forcalculation. In other words, the write power at which modulation getseffectively 0 (the X intercept in the graph is 0) may be obtained byextrapolating from a graph showing the relationship between the writepower and the modulation. Depending on the formula of calculation usedor the number of measurement data, the write power P0 at whichmodulation gets 0 may move to some extent. However, in such a case, P0is still in a sufficient range of error for calculating the optimumpower.

According to the present invention, which enables to enhance theprecision of test writing, it is possible to provide a high-speedoptical disk of a better recording quality.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 2 is an illustration showing an example of recording pulse strategyused in the present invention.

FIG. 3 is a graph showing the relationship between the write power andthe modulation according to an embodiment of the present invention.

FIG. 4 is an illustration showing an example of recording pulse strategyused in the present invention.

FIG. 5 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 6 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 7 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 8 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 9 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 10 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 11 is a graph showing the relationship between the write power andβ according to an embodiment of the present invention.

FIG. 12 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 13 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 14 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 15 is a graph showing the relationship between the write power andβ according to an embodiment of the present invention.

FIG. 16 is an illustration showing an example of device used in thepresent invention.

FIG. 17 is an illustration showing an example of device used in thepresent invention.

FIG. 18 is an illustration showing an example of device used in thepresent invention.

FIG. 19 is a graph showing the relationship between the write power andthe constant p according to an embodiment of the present invention.

FIG. 20 is a graph showing the relationship between the write power andthe constant p according to an embodiment of the present invention.

FIG. 21 is a graph showing the relationship between the write power andthe constant p according to an embodiment of the present invention.

FIG. 22 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 23 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 24 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 25 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 26 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 27 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 28 is a flowchart showing a test writing method according to anembodiment of the present invention.

FIG. 29 is a graph showing the relationship between the write power andthe jitter according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

We will describe below the embodiments of the present invention withreference to drawings.

To begin with, we will describe the recording method used in the presentinvention. For writing data on an optical disk, the multi pulse markedge recording method will be used to write data on the disk to providethe information on the length of marks and spaces. And a modulationmethod combining mark lengths ranging from 3T to 14T and space lengthsranging from 3T to 14T is used.

FIG. 2 shows an example of a write strategy used in the presentinvention. In the present embodiment, a 2T strategy is used. 3T mark isformed by a single pulse, and 4T mark and 5T mark are formed by twopulses, the first pulse and the last pulse. 6T mark and 7T mark arecomposed of three pulses consisting of the first pulse, the last pulseand a middle pulse. And 8T mark and 9T mark are composed of fourrecording pulses in total consisting of the first pulse, the last pulseand two middle pulses. Thereafter, as the mark length becomes longer,the number of middle pulses increases. Here, when the recording mark isrepresented by nT (T represents the reference clock frequency and nrepresents a natural number of two or more), an even number length marksuch as 4T and 6T is represented by nT =2LT, and an odd number lengthmark such as 3T and 5T can be represented by nT=(2L+1)T, wherein L is anatural number and represents the number of recording pulses.

For the disk, a rewritable DVD (a phase change type disk adapted to redlight source) capable of 8× recording is used, and a drive with asemiconductor laser of 660 nm wavelength is used for reproducing andmeasuring recordings. Linear velocity is set at approximately 27.9 m/s.The clock frequency T in FIG. 2 is approximately 4.8 ns.

A flowchart describing the operation of the test writing methodaccording to the present embodiment is shown in FIG. 1, and we willdescribe the present invention with reference to the same. In the firststep (S101), we read the recommended write power, the pulse width andother recording conditions recorded in the disk, and as a result weobtained a write power (Pw) of 38 mW, an erase power (Pe) of 8 mW, and abias power (Pb) of 0.1 mW in the form of laser power. For the secondstep (S102), we set the laser power conditions in the vicinity, and forthe third step (S103-S108) we conducted test writings on the disk. Asfor the laser power conditions, fixing the Pb value, and taking theratio between Pw and Pe (Pw/Pe) as fixed values, we changed the writepower from 0.4 times to 1.2 times of the recommended write power, inother words from 15.2 mW to 45.6 mW. As for erase power Pe, togetherwith Pw, we changed them from 3.2 mW to 45.6 mW. At this time, weconducted separate test writings by using two types of test writingwrite patterns consisting of a write pattern composed of only evennumber length marks and another composed of only odd number lengthmarks. In the third step (S103) we conducted test writings several timesby using a test writing write pattern composed of even number lengthmarks and by changing the write and erase power, and in view of therelationship between the write power and the modulation obtained in thethird step, in the fourth step (S104) we obtained 17.5 mW as the writepower P0 (even) at which modulation gets 0. In the fifth step, wemultiplied P0 (even) by 2.1 as the constant p and obtained a write powerfor even number length marks Pw (even) of 36.8 mW.

Similarly, we recorded by using a write pattern for test writingcomposed of odd number length marks, obtained the relationship betweenthe write power and the modulation (S106), and determined the writepower P0 (odd) at which modulation gets 0 (S107). Then, we multiplied P0(odd) by the constant p of 2.1 and obtained 38.9 mW as the write powerfor odd number length mark Pw (odd).

For the ninth step (S109) we recorded by using a write pattern for testwriting in which even number length marks and odd number length marksare mixed by using the write power for odd number length marks and thewrite power for even number length marks obtained from the third stepthrough the eighth step, and for the tenth step (S110) we confirmed therecording ability and we obtained a sufficient jitter for practical useof 5.1%.

For comparison with the prior method, we obtained a write power P0 atwhich modulation gets 0 by using a write pattern for test writing inwhich even number length marks and odd number length marks are mixed,multiplied the P0 by the constant p=2.1 and as a result we obtained awrite power Pw=37.8 mW. When we recorded and reproduced by maintainingthe write power for both even number length marks and odd number lengthmarks at the same level of 37.8 mW, the jitter was 6.5%. On the otherhand, we could obtain a better recording ability by setting separatelythe write power for even number length marks and for odd number lengthmarks.

In the present embodiment, as a good jitter could be obtained at theninth step, it was unnecessary to proceed to the eleventh step (S111).However, when a good jitter cannot be obtained in S110, it is better tofine adjust Pw (odd) and Pw (even).

The test-write patterns for even number length/odd number length marksused in the present embodiment are composed of even number length/oddnumber length marks only in their marks and their space part may becomposed of a mixture of even number length and odd number length. Inother words, with regard to the space length, it is unnecessary to setany restrictions such as providing even number length of spaces fortest-write patterns for even number length marks.

In the present embodiment, we set the constant p for multiplying thewrite starting power P0 at 2.1. When we made the constant p smaller than1.5, as FIG. 19 shows, the reproduction jitter worsened rapidly becauseit was no longer possible to obtain a sufficient amplitude, and whenp=1.2, the reproduction jitter worsened to 13.0%. And with p=3.3, thejitter stood at 12.8%, and thus when the constant p is made larger than3.0, the jitter worsened considerably. This is due to an expansion ofthe recording mark width to such an extent as the effect of crosserasure cannot be ignored. Therefore, it is preferable that the constantp be larger than 1.5 and smaller than 3.0. Furthermore, when theconstant p is set at 2.0, the jitter obtained after several testwritings was within a good range of 5.1-6.0%. When we chose a constant psmaller than 2.0, for example a value of 1.8, the range of jitterobtained after several test writings expanded to 5.4-7.0% and at thesame time the maximum jitter grew larger (FIG. 20). When the constant pis smaller than 2, the effect of the jitter having grown larger due tothe development of a write power offset and the like because of dust,stains or some other causes will be considerable. Therefore, it is morepreferable that the constant p be larger than 2.0. And FIG. 21 shows therelationship between the jitter obtained after 500 multiple recordingsand the constant p. When p grows larger than 2.8, the recording film isdestroyed due to overpower and the jitter worsens. By keeping p notlarger than 2.8, it is possible to prevent irradiation by overpower andto prevent any deterioration of performance due to multiple rewritings,and therefore it is more preferable.

In the 2T strategy, the number of recording pulses of a pair of adjacenteven number length marks and odd number length marks are equal. Forexample, as FIG. 2 shows, each 4T mark and 5T mark are respectivelycomposed of two recording pulses, and each 6T mark and 7T mark arerespectively composed of three recording pulses. What is characteristichere is that the pulse width (W1) at the Pb level after the irradiationof the first pulse of the 4T mark and that (W1) of the 6T mark havenearly the same length, and similarly the pulse width (W2) at the Pblevel after the irradiation of the first pulse of the 5T mark and that(W2) of the 7T mark have nearly the same length. The position of thefront edge of the recording mark formed by the first pulse is affectedby the beginning position of the recording pulse following the firstpulse. For example, when the recording pulse following the first pulseare far from the first pulse, due to the narrowing of the region thatwill be re-crystallized after the melting of the recording film, thefront edge position shrinks little and is fixed at a position near thefront edge of the melting region. On the contrary, when the recordingpulses following the first pulse approach the first pulse, due to theexpansion of the region that will be re-crystallized after the meltingof the recording film, the front edge position shrinks violently and thefront edge position will be fixed after the melting region.

It is considered that 4T marks and 6T marks as well as 5T marks and 7Tmarks are respectively affected in the same way in terms of the impactof irradiation of the recording pulses following the first pulse (middlepulses or the last pulse) on the front edge position. As FIG. 2 shows,8T mark will have a front edge position similar to that of 4T and 6T.The use of such write patterns for test writing composed solely by markshaving similar thermal characteristics makes it difficult to see thegrowth of jitter due to changes in the edge position resulting from theshape of recording pulses of a plurality of types, it will be possibleto obtain accurately and effectively the optimum recording pulse width.

In the present embodiment, as FIG. 2 shows, with regard to the 3T markformed by a single pulse, we set independently the recording pulseconditions including the first pulse position. The reason is that, asthe 3T mark is composed of a single pulse, the process by which thefront edge position is determined is different from that of other markscomposed of a plurality of recording pulses. In the present embodiment,in the test writing of step S109, the recording pulse conditions of the3T mark are obtained at the same time as obtaining ΔT in the 10^(th)step (S110).

And in the present embodiment, we set an equal number of recordingpulses for nT=2LT and nT=(2L+1)T so that 4T mark and 5T mark may becomposed of a same number of pulses. On the other hand, when therecording pulses for nT=2LT and nT=(2L−1)T are equal so that 5T and 6Tmay have a same number of pulses, the present invention is effective inthe same manner.

And, in the present embodiment, the power P0 (even) and P0 (odd) atwhich modulation gets 0 are multiplied by a constant p for calculatingthe write power for even number length marks and for odd number lengthmarks. However, when the relationship between the modulation and thepower is largely different between the time of recording even numberlength marks and the time of recording odd number length marks, adifferent value may be used for the multiplication value p. In otherwords, depending on the characteristics of the medium, the constant pmay be set at different values, one for the even number length marks andanother for odd number length marks.

And in the present embodiment, we set Pw (even) by multiplying the writepower P0 for effectively at which modulation gets 0 by a constant p.However, instead of the modulation 0, we may seek a Pw′ at whichmodulation gets a predetermined value between the modulation 0 and thesaturated modulation, and may obtain Pw by multiplying the Pw′ by aconstant p′. An example is shown in FIG. 28. FIG. 28 shows the testwriting method when the predetermined modulation is set at 35%. It ispreferable that the set modulation be within a range of 25% to 40%wherein the variation of modulation is sharp in relation to thevariation of the write power and the writing does not get blurred. Asharp variation of the modulation in relation to the write power meansthe possibility of setting accurately the write power. The constant p′is a constant set by the disk or drive used, and it may be often1.2≦p′≦2.5. In the case of the drive and medium used in the presentembodiment, we calculated by taking Pw′ (even) obtained in the stepS1804 of FIG. 28 as being equal to 23.0 mW, and Pw′ (odd) as being equalto 24.3 mW, and setting p′=1.6 we calculated Pw (even) as being equal to36.5 mW, and Pw′ (odd) as being equal to 38.9 mW. When we confirmed therecording ability in step S1810, the jitter stood at 5.1% and we couldobtain a practically passable recording ability. Thus, the write powervalue calculated respectively from P0 and Pw′ do not necessarilycoincide. When the recording ability is not found to be sufficient as aresult of the confirmation of the recording ability in the step S110 ofFIG. 1 or the step S1810 of FIG. 28, it is preferable to fine adjust thesame in the step S111 of FIG. 1 or the step S1811 of FIG. 28.

Embodiment 2

In the embodiment 1, we used the so-called 2T strategy wherein thenumber of recording pulses in the adjacent even number length marks andodd number length marks is the same. However, in the present embodiment,the case of using 3T strategy is shown. The 3T strategy is a strategywherein the number of recording pulses of the marks represented bynT=3LT, nT=(3L−2) T and nT=(3L−1) T are the same. In this strategy, L isa natural number and represents a number of recording pulses. Forexample, 4T-6T marks are respectively composed of two recording pulses,and 7T-9T marks are respectively composed of three recording pulses.Such a 3T strategy is shown in FIG. 4 (in the embodiment 2, however, thewrite strategy composed of 3T-14T is used).

In the present embodiment, a rewritable DVD capable of 10× recording isused for the optical disk, and a drive provided with a semiconductorlaser of a wavelength of 660 nm is used for recording, reproduction andmeasurement. This drive is capable of setting the maximum of threelevels for the write power Pw level. We set its linear velocity at 34.9m/s. The 3T strategy, like the 2T strategy, includes three types ofpattern consisting of a write pattern for test writing composed ofnT=3LT marks, a write pattern for test writing composed of nT=(3L−2) Tmarks and a write pattern for test writing composed of nT=(3L−1) Tmarks, and we obtained the relationship between the write power and themodulation when each write pattern is used for recording according tothe flowchart of FIG. 5.

To begin with, for the step S201, we read the recommended write power,pulse width and other recording conditions recorded in the disk, andobtained a write power (Pw) of 56 mW, an erase power (Pe) of 11 mW, abias power (Pb) of 0.3 mW in the form of laser power. For the step S202,we set the laser power conditions in the vicinity, and for the stepsS203-S211, we conducted test writing on a disk. As for the laser powerconditions, we fixed the Pb value, and we varied the write power from0.4 times to 1.2 times of the recommended write power, in other wordsfrom 22.4 mW to 67.2 mW taking the ratio between Pw and Pe (Pw/Pe) as afixed value. As for the erase power Pe, we varied the same along with Pwfrom 4.4 mW to 13.2 mW. At this time, we conducted separate testwritings by using two types of write patterns for test writing, i.e. awrite pattern composed solely of even number length marks and anotherwrite pattern composed solely of odd number length marks. In the stepS203, we conducted several test writings by using a write pattern fortest writing composed of nT=3LT marks and by changing the write anderase powers, and the relationship between the write power and themodulation that we obtained in the step S203 served as the basis of avalue of 20.9 mW that we obtained as the write power P0 (3LT) at whichmodulation gets 0 in the step S204 when we recorded a write pattern fortest writing composed of nT=3LT marks. Similarly, in the step S207, weobtained 19.1 mW as the write power P0 ((3L−2)T) at which modulationgets 0 at the time of recording the nT=(3L−2) T marks, and in the stepS210, we obtained 20.2 mW as the write power P0 ((3L−1)T) at whichmodulation gets 0 at the time of recording the nT=((3L−1)T). Then, wemultiplied each P0 by 2.8 for the constant p and obtained 58.5 mW forthe write power Pw (3LT), 53.5 mW for Pw (3L−2)T), and 56.6 mW for Pw((3L−1)T) (steps S205, S208, S211).

In the step S212, using the three types of write powers obtained asdescribed above, we recorded a write pattern for test writing whereinmark length and space length from 3T to 14T are arranged at random, andin the step S213 as a result of our confirmation of the recordingability, we could obtain a practically passable jitter of 7.5%. Further,in the step S214, we could contain the jitter to 7.0% by fine-tuning Pw(3LT) from 58.5 mW to 59.1 mW.

In the present embodiment we set the constant p at 2.8. However, as weincreased the constant p to larger than 2.8, the allowable maximumfrequency of rewriting decreased. For example, when the initial randomsignal jitter is compared, with p=2.8, its value was 7.5%, and withp=3.0, it was 8.1% and thus both values were practically passable. Withp=2.8, however, the reproduction jitter did not change and constitutedpractically no problem until the frequency of rewriting reached 1,000times. With p=3.0, however, at the 800^(th) rewriting, the jitter valueexceeded 13%. Therefore, it is preferable to keep the value of p=2.8 orless.

And in the present embodiment, we used jitter as a factor of assessmentof the reproduction characteristic. However, any change in the type offactors of assessment brought about no change in the effect of thepresent invention. For example, PRML and the like may be used for theevaluation of its reproduction performance.

Actual user data were recorded by using the write power obtained as aresult of these test writings.

Embodiment 3

In the embodiment 1, we conducted respective test writing by dividingthe write patterns for test writing between the even number length marksrepresented by nT=2LT and the odd number length marks represented bynT=(2L+1)T, multiplied the respective write power P0 at which modulationgets 0 with a constant p and as a result obtained the optimum writepowers for the odd number length marks and the even number length marks.In the present embodiment, we will show a method of seeking therelationship between the modulation and the write power by varyingsubstantially the write power for only one test-write pattern, seekingthe write power of the other write pattern in such a way that the latterwrite power may be nearly the same as the modulation at the write powersought, and thus setting the write power.

In the present invention, we used a write strategy similar to theembodiment 1, a rewritable-type DVD disk capable of 8× recording and adrive provided with a semiconductor laser with a wavelength of 660 nm.We set its linear velocity at approximately 27.9 m/s.

A flowchart describing the operation of the test writing methodaccording to the present embodiment is shown in FIG. 6, and we willdescribe the present invention with reference to this figure. The stepsS301 through S305 are similar to FIG. 1, and we will omit detaileddescriptions thereof. Like in the embodiment 1, in the step S304, weobtained 17.5 mW as the write power P0 (even) at which modulation gets0. In the step S305, we multiplied P0 (even) with 2.1 for the constant pand obtained 36.8 mW as the write power Pw (even) for even number lengthmarks. In addition, we calculated the modulation mod (even) for a writepower of 36.8 mW and obtained mod (even)=59%.

In the following step S306, we recorded by using a test-write patterncomposed of odd number length marks represented by nT=(2L+1)T and awrite power Pw (even) of 36.8 mW, and when we calculated the modulationmod at the moment, we found that it was 57%. As the modulation mod for atest-write pattern composed of odd number length marks was smaller thanmod (even)=59%, we proceeded from the step S308 to the step S310. Werecorded a test-write pattern composed of odd number length marks with apower higher than 36.8 mW. At this time, we recorded by changing thewrite power Pw up to 1.2 times of Pw (even). In the present embodiment,we changed Pw by taking Pw=Pw (even)+Pw (even)*0.02×, (1≦x≦10). As aresult, the modulation stood at 59% when Pw=39.7 mW for x=4 andtherefore we chose Pw (odd)=39.7 mW. Although the modulation was 59%even when Pw=40.5 mW for x=5, in the present embodiment, we chose thewrite power at which the desired modulation can be obtained and the oneclosest to Pw (even) as Pw (odd).

In the step S311 we recorded by using a write pattern for test writingwherein even number length marks and odd number length marks were mixedand by using the write power for odd number length marks Pw (odd) andthe write power for even number length marks Pw (even), and in the stepS312 we confirmed the recording ability. As a result, we could obtain apractically sufficient jitter 5.4%.

In the present embodiment, we sought the modulation for the write powerwe had sought by test writing of even number length marks, and set thewrite power for odd number length marks in such a way that the samemodulation may be achieved. On the contrary, even if a modulation soughtby test writing an odd number length mark, and the write power of aneven number length mark is set in such a way that the modulation may benearly the same as the modulation sought, the effect of the presentinvention remains unchanged. And not only in the case of 2T strategy,but also in the case of 3T, 4T strategy and a plurality of other typesof write patterns for test writing, the similar effect can be obtained.Specifically, in the case of 3T strategy, the write power P0 (3LT) issought by using a write pattern formed by nT=3LT marks, P0 (3LT) ismultiplied by a constant p to obtain the optimum write power Pw (3LT).The write power Pw (3L−2) and Pw (3L−1) are respectively set in such away that the modulation existing at the time when a write patterncomposed of the nT=(3L−2) marks is recorded and the modulation existingat the time when a write pattern composed of the nT=(3L−1)T marks isrecorded may be the same as the modulation mod (3LT) existing at thetime when a write pattern composed of the nT=3LT is recorded with Pw(3LT).

In the present embodiment, a test writing starts with a write patterncomposed of even number length marks, but this is only an example, andeven if a test writing starts with a write pattern composed of oddnumber length marks, Pw (odd) is sought and then Pw (even) is sought,the effect of the present invention does not change.

Further, in the present embodiment, Pw (even) is set by multiplying thewrite power P0 at which modulation gets effectively 0 by a constant p.However, instead of a modulation that gets 0. a Pw′ having thepredetermined value between the modulation 0 and the saturatedmodulation may be sought and the Pw′ may be multiplied by the constantp′ to obtain Pw. FIG. 22 shows an example thereof. FIG. 22 shows amethod of test writing when the predetermined modulation is set at 40%.Further FIG. 23 shows an example of calculating Pw from the write powerwhen the jitter reached the predetermined value. The generalrelationship between the jitter and the write power is shown in FIG. 29.In the case of FIG. 23, the jitter value existing at the time ofrecording by changing the write power, and the write power Pw″ (even)existing when the jitter reached 13% is multiplied by the constant p″ toobtain the write power Pw (even). When a device and a disk similar tothose of the present embodiment are used, it is preferable to set thepredetermined jitter between 13% and 17%. And when a limit equalizer isused, it is preferable to set the predetermined jitter between 6% and10%. The constant p″ is also a constant set by the disk or drive used,and it is often 1.2≦p″≦2.0.

As described above, the method of determining the writer power of afreely chosen write pattern may be calculated from a write power P0 atwhich modulation effectively gets 0, or may be calculated by apredetermined modulation (for example 40% as shown in FIG. 22) or may becalculated from the jitter. Obviously, these methods are not limitative,and the write power of any write pattern may be chosen by apredetermined method.

Embodiment 4

In the present embodiment, an example of test writing by the 2T strategywill be described with reference to FIGS. 7 and 8. The drive and opticaldisk used are the same as those in the embodiment 1, and the descriptionof operations (steps) common with the embodiment 1 will be omitted.

In the embodiment 3, we sought a Pw (odd) that takes nearly the samemodulation as mod (even), and then we confirmed the recording ability ofthe method by using a test-write pattern wherein even number lengthmarks and odd number length marks are mixed. Here, we used the methodshown in FIG. 7. In other words, we used the method of obtaining Pw(even), and instead of using a test-write pattern composed of odd numbermarks, using a test-write pattern wherein odd number length marks andeven number length marks are mixed for obtaining directly Pw (odd) witha good recording ability. In the present embodiment, in the step S406 werecorded a write pattern wherein even number length marks and odd numberlength marks are mixed by varying the write power from 29.4 mW to 44.1mW centered around the write power for even number length marks Pw(even)=36.8 mW obtained in the step S405. As a result, in the step S407we obtained 39.0 mW as the Pw (odd) at which the jitter is reduced tothe minimum. At this time, the jitter resulting from the recording of amixed pattern was 5.2%, which was a practically good performance.

The write power Pw to be varied in the step S406 was from 0.8 times ormore to 1.2 times or less of the write power for even number lengthmarks Pw (even), or a*Pw (even)≦Pw≦b*Pw(even), and it is preferable thatit be 0.8≦a≦1.0, 1.0≦b≦1.2. If a is smaller than 0.8, the insufficiencyof the write power is evident and therefore it will be a useless testwriting for test writings according to the present method, and it mayconstitute a waste of the limited drive test zone. And if b is largerthan 1.2, as FIG. 3 shows, although the modulation is not very differentfrom the optimum write power, it will constitute an overpower and maygive rise to such phenomena as the deterioration of repeated rewritingcapacity. Thus, it is not preferable.

FIG. 8 shows an example of the means for reducing the frequency of testwritings conducted in FIG. 7. According to the test writing shown inFIG. 8, a or b of FIG. 7 corresponds with the case of 1.0 and thereforethe zone required for test writing can be reduced, and the time requiredfor test writing can be curtailed.

FIG. 7 or 8 indicates the write power to be chosen for minimizing thejitter. And it may be the central value within the range of write powerwhere the jitter may be less than the predetermined value of, forexample, 13%. Or it may be PRML instead of the jitter index. The presentinvention does not limit the index of recording ability to jitters.

And in FIGS. 7 and 8, Pw (even) is calculated based on P0 (even). Butthe means of calculating Pw (even) is not limited to this. FIG. 24 showsan example of calculating Pw by seeking the write power Pw′ by which themodulation reaches 40% and by multiplying this Pw′ with a constant p′.Thus, the means of calculating the write power in any freely chosenwrite pattern among a plurality of write patterns is not limited to onlyone, and it is preferable to choose one according to the drive, mediumand specific use.

Embodiment 5

In the present embodiment, we will describe an example of test writingsuitable for a medium wherein a certain relationship exists between thewrite power used for even number length marks and the write power usedfor odd number length marks with reference to FIG. 9. The drive, opticaldisk used and the like are similar to those of the embodiment 2, and itslinear velocity is set at 34.9 m/s. And here we used the 2T strategy andnot the 3T strategy used in the embodiment 2. The steps S601 to S603 aresimilar to the embodiment 2 except that the 2T strategy is used for thewrite strategy and are therefore omitted here. By recording in the stepS604 a write pattern for test writing composed of even number lengthmarks, we obtained 20.0 mW as a write power P0 (even) at which themodulation gets 0. Then, in the step S605 we multiplied P0 (even) by aconstant p of 2.8 to obtain 56.0 mW as the write power Pw (even).

Then, in the step S606, the write power for odd number length marks isset. For the combination of the disk and the recording conditions usedin the present embodiment, the equation of Pw (odd)=q×Pw (even) issuitable, and we obtained the best recording performance when theconstant q was set at 0.96. However, in the present embodiment where anequation of Pw (odd)=q×Pw (even) is suitable, depending on the diskstructure and the write strategy used, the equation of Pw (odd)=Pw(even)+r may sometimes be preferable. The question of which equation tochoose may be determined at the time of shipping the drive in advance bythe type of the medium. Or, the suitable equation may be chosen when themedium is loaded for the first time.

After setting in the step S606 the Pw (odd) at 53.8 mW from the equationof Pw (odd)=0.96×Pw (even), in the step S607 we used the write power foreven number length marks as Pw (even) and the write power for odd numberlength marks as Pw (odd) for recording a test-write pattern wherein oddnumber length marks and even number length marks are mixed and evaluatedthe recording ability (step S608). And as a result, we obtained apractically passable recording ability of jitter=7.8%.

The establishment of a correlation by means of a mathematical formulabetween the write power Pw (odd) for recording a write pattern composedof odd number length marks and the write power Pw (even) for recording awrite pattern composed of even number length marks simplifies theprocess of test writing because only one of the write patterns needs tobe tested, and thus the time required for test writing can besubstantially curtailed. The values of the constant q and the constant rmay be chosen just before shipping the drive. Or the values of q and rmay be obtained by learning when the medium is loaded for the firsttime, and the medium ID and q and r may be correlated. When we conductedtest writings by combining several types of media and write strategies,we obtained good recording abilities within a range of 0.9 to 1.1 forthe constant q and the range of −3.0 to 3.0 for the constant r.

In the present embodiment, we calculated Pw (even) based on P0 (even),but the means of calculating Pw (even) is not limited to this. Thejitter performance may be chosen as an index, and PRML may be chosen asthe basis of such calculation. FIG. 25 shows an example of seeking awrite power Pw (even) at which β is brought to approximately 5%. It ispreferable to apply the present method to media wherein β changessharply in relation to variations in the write power. In FIG. 25 thevalue of β is set at 5%. However, depending on the property of themedium and drive, it is preferable to set the optimum value of β. Thepresent method of calculating Pw based on the value of β is advantageousin that the write power can be obtained with a high precision incomparison with the method of calculating from P0 shown in FIG. 9,because the desired write power can be directly obtained. Thus, themeans of calculating the write power for any freely chosen write patternfrom among a plurality of write patterns is not limited to only one, andit is preferable to choose one depending on the drive, medium and usethereof.

In the present embodiment, we used the 2T strategy, but the 3T strategyand the 4T strategy are also effective test writing methods. The methodof correlating a plurality of write patterns by a mathematical formula,conducting test writings on a write pattern and seeking the write powerof other write patterns by a predetermined mathematical formula isadvantageous in that the time required for test writing and the drivetest zone can be curtailed.

Embodiment 6

In the embodiments 1-5, we sought the optimum write power by usingmodulation for an index. In the present embodiment, we will describe atest writing method of setting the optimum write power not by usingmodulation but by using β.

In the present embodiment, we used a blue light source compatible diskcapable of 6× recording. We set its linear velocity at 31.7 m/s and useda write strategy composed of 2T-9T marks. A flowchart describing theoperation of the test writing method according to the present inventionis shown in FIG. 10. To begin with, in the step S701 we read therecommended write power and other recording conditions recorded on thedisk, and obtained 18 mW for the write power (Pw), 3.4 mW for the erasepower (Pe), and 0.1 mW for the bias power (Pb). In the step S702, we setthe laser power conditions in the vicinity, and in the steps S703 andS705 we conducted test writings on the disk. As for the laser powerconditions, we fixed the Pb value at 0.1 mW, fixed the Pe and Pw ratio,and varied Pw by the step of 0.2 mW between 15 mW and 21 mW. At thistime, in the step S703, we used test-write patterns including 2T mark,the shortest mark among the even number length marks, and in the stepS705 we used test-write patterns including 3T mark, the shortest markamong the odd number length marks. Specifically, the patterns used inthe step S703 are write patterns composed of 2T marks and 8T marks andspaces of length varying from 2T to 9T, and the patterns used in thestep S705 are write patterns composed of 3T marks and 8T marks andspaces of length varying from 2T to 8T. Thus, the arrangement of acommon mark length (here 8T mark) in the write pattern is advantageousin that β of the 2T and 3T marks constituting respectively the smallestmark can be calculated on the basis of the same 8T mark. In the stepsS703 and S705 we recorded by changing the write power and calculatedrespectively β(2T) whichs β of the 2T mark and β(3T) whichs β of the 3Tmark. FIG. 11 shows the relationship between the write power and β(2T)and β(3T). Thus, the relationship between β and the write powergenerally differs depending on the length of marks.

In the present embodiment, taking the desired β as 0, we set in thesteps S704 and S706 the write power at which β(2T) =0 at Pw (even)=18.2mW, and the write power at which β(3T) =0 at Pw(odd)=18.4 mW. Then, inthe step S707 we recorded a test-write pattern (confirming pattern)wherein nT=2LT marks and nT=(2L+1) T marks are mixed at 18.2 mW for thewrite power Pw (even) for nT=2LT marks and at 18.4 mW for the writepower Pw (odd) for nT=(2L+1) T marks. As a result, the jitter stood at4.9% representing a good value presenting practically no problem.

In the present embodiment, we test wrote separately the odd numberminimum length mark and the even number minimum length mark. However, asFIG. 12 shows, the write power for odd number length marks Pw (odd) andthe write power for even number length marks Pw (even) at which β(2T)and β(3T) get the desired value may be sought by using write patternsincluding 2T and 3T, for example random patterns, recording them bychanging write power, and thus detecting and obtaining separately β(2T)and β(3T).

In the test writing method shown in the present embodiment, it isimportant to set respectively the write power in such a way that theasymmetry of the minimum mark and the next large mark or β or γ may benearly equal, and the difference of the modulation method of whether the2T mark is the minimum or the 3T mark (the dimension of the minimummark) is not important. Therefore, even the modulation method whereinthe 3T mark becomes the minimum does not change the effect of thepresent invention. Here, the expression “nearly equal” does not meanprecisely the same value, and for example the term “asymmetry” means anallowable range of ±1%. The nearest asymmetry in the range of settingstage of the write power or β or γ may be chosen for the setting.

Embodiment 7

In each of the embodiments 1-6, we have described an example of testwriting methods in the case where the laser driver of each drive canchoose any one of the desired multiple levels of write power Pw. Here,we will show an example of test writing in the case where the laserdriver has not the desired set number of Pw levels.

A flowchart describing the operation of the test writing methodaccording to the present embodiment is shown in FIG. 13, and we willexplain with reference to the figure. As for the optical disk, we usethe same one as that of the embodiment 1, and for recording,reproduction and measurement, we used a drive provided with asemiconductor laser with a wavelength of 660 nm. On this drive, only avalue of Pw level can be set. As the steps S901-S908 of FIG. 13 areidentical to the steps S101-S108 of FIG. 1, the description here isomitted. In the step S905, by the steps up to S908, we obtained a writepower for even number length marks Pw (even) of 36.8 mW and in the stepS908 we obtained 38.9 mW as the write power for odd number length marksPw (odd).

In the present embodiment, taking the value obtained by dividing thedifference between Pw (even) and Pw (odd) by the mean value of thesewrite powers as the parameter x, we decided to choose the method of testwriting by the magnitude of its value. In the step S909, we divided IPw(even)−Pw (odd)|whichs the difference between Pw (even) and Pw (odd) bythe mean value of two write powers represented by (Pw (even)+Pw(odd))/2. As a result, the parameter x according to the presentembodiment turned up to be 5.5%, and following the determination of thestep S910, we proceeded to the step S914.

In the step S914, we used the calculation equation to calculate thewrite power Pw (opt). The calculation equations used here include forexample the following equations.

Type 1. Pw (opt)=Pw (even)

Type 2. Pw (opt)=Pw (odd)

Type 3. Pw (opt)=(Pw (even)+Pw (odd))/2

Type 4. Pw (opt)=Max (Pw (even), Pw (odd))

Type 5. Pw (opt)=Min (Pw (even), Pw (odd))

Type 1 is a calculation equation attaching importance to the even numberlength marks, and is suitable for the case where the modulation methodwith 2T mark being the minimum mark is adopted. Type 2 is a calculationequation attaching importance to the odd number length marks and issuitable for the case where the modulation method with 3T mark being theminimum mark is adopted. And Type 3 takes the average write power of Pw(even) and Pw (odd) as the optimum write power Pw (opt) and isadvantageous in that the variation at the time of recording is reduced.Type 4 is a calculation equation of choosing a write power whichever islarger among the Pw (even) and the Pw (odd) for the optimum power Pw(opt). Type 4 is suitable in the case where importance is attached toS/N such as in the case of using a medium with a low S/N ratio hoping toobtain a gain in modulation. On the contrary, Type 5 is a calculationequation of choosing a write power whichever is smaller among the Pw(even) and the Pw (odd) for the optimum power Pw (opt), This is suitablefor a medium wherein marks cannot be recorded widely due to a high levelof crosstalk from the adjacent tracks. In other words, when jitterdeterioration is severe due to crosstalk, the calculation formula ofType 5 is suitable. These calculation equations may be chosen accordingto the type of the drive or disk used. And the calculation equationslisted above are only some of the examples, and the use of equations forseeking the optimum write power Pw (opt) from among the Pw (even) andthe Pw (odd) is within the scope of application of the presentinvention.

In the present embodiment, we used Type 3. Since Pw (even)=36.8 mW andPw (odd)=38.9 mW the optimum write power Pw (opt) will be Pw(opt)=(36.8+38.9)/2=37.9 mW. Using Pw (opt) calculated in the step S914,we conducted in the step S915 test writings by using random patterns,and the jitter obtained was 6.5%, representing a practically passablerecording ability.

In the present embodiment, as the criteria of judgment in the step S910,we chose that of whether the parameter x was larger than 10% or not.However, in order to insure the safety of records, the threshold valuemay be set at for example 5%. It is preferable to set the thresholdvalue according to the drive and the medium used. When the thresholdvalue is set at 5%, in the present embodiment, in the step S910 of FIG.13 a determination of “Yes” is given, and the process will proceed tothe step S911. As the drive used in the present embodiment has no pulsevariable function, a “No” determination is given in the step S911, itwill be NG, or write error. The occurrence of such a write error mayapparently seem disadvantageous for the user. However, as a result ofirradiating an inadequate write power in an attempt to record, datarecorded before or data contained in the management area may bedestroyed. It is an important process to prevent such data destruction,and can protect recorded information constituting the assets of users.FIG. 13 showed an example of NG when a No determination is given in thestep S911. However, when a No determination is given in the step S911,the process of proceeding to the step S914 to find Pw is acceptable as amatter of course. In such a case, instead of keep trying to find Pwuntil a sufficient recording ability can be obtained in the step S916,it is preferable to set a frequency of retrials z in the step S917. Thefrequency of retrials may be determined according to the drive and themedium used. In the present embodiment, we chose z=1.

And in the present embodiment, in the step S909 we sought the parameterx from the following formula.x=|Pw(even)−Pw(odd)|/(Pw (even)+Pw (odd))/2However, the present invention is not limited to the formula shownabove, and any mathematical formula capable of showing in any form thedifference between the optimum power of even number length marks and theoptimum power of odd number length marks may be adopted.

In the present embodiment, as the drive was not pulse width variabletype, a No determination was given in the step S911. When a pulse widthvariable type drive is used, it will be possible to vary pulse width inthe step S912. For example, as in the present embodiment, in the case ofPw (even)<Pw (odd), it is preferable to expand the pulse width of oddnumber length marks in write once media. Generally in write once mediamarks grow larger proportionately to the energy irradiated. Therefore,it is possible to reduce write power by expanding pulse width, and as aresult, a power close to Pw (even) may be used. On the contrary, thenarrowing of the pulse width of Pw (even) produces the same effect.Further, in rewritable media it is better to narrow the pulse width ofodd number length marks. In rewritable phase-change media, thecrystallization of molten zone called “re-crystallization” occurs. Ifpulse width is large, crystallization intensifies, and the injection oftoo much energy can reduce amplitude. In such a case, it is possible toincrease amplitude by narrowing pulse width. It is preferable to changepulse width by the step of approximately 1 ns. This will be equal to thetime roughly corresponding to the rising time or falling time of laser.Or pulse may be made variable by dividing Tw by n so that it may beshown for example as Tw/16, and in either case the lot variation of themedium or the individual variation of the laser driver may be absorbed.

In the present embodiment, we set Pw based on the write power P0 atwhich modulation gets effectively 0. However, instead of modulation 0,the method of seeking Pw by seeking a write power Pw′ at which thepredetermined modulation is obtained and multiplying the Pw′ by aconstant p′ may be used. An example thereof is shown in FIG. 26. FIG. 26shows a test writing method applicable when the predetermined modulationis set at 30%. The present embodiment describes the case where the laserdriver has no desired number of write power level set, and the testwriting method shown in FIGS. 13 and 26 may be used as a test writingmethod on a drive on which the desired write power level can be set. Inthis case, when a low quality optical disk medium incapable of assuringproper recording ability is inserted in the drive, it will be a methodof ejecting the same as NG.

Embodiment 8

In the embodiment 7, we described the case where the 2T strategy is usedon a drive having only a level of Pw. In the present embodiment, we willdescribe the case where the 3T strategy is used on a drive having twolevels of Pw. On a drive on which two Pw levels can be set, in the 2Tstrategy write power can be allocated respectively on the even numberlength marks and on the odd number length marks. However, when the 3Tstrategy is used, it will not be possible to allocate write power levelsrespectively on three types of write patterns. Even in such a case, itwill be possible to set write power by a process similar to FIG. 13. Forexample, we will describe an example of using the 3T strategy on a driveon which two write powers, Pw (A) and Pw (B), can be set with referenceto FIG. 14.

As for the optical disk, we used a 10× rewritable DVD and as for thedrive, we used the same drive as the embodiment 1. As the stepsS1101-S1111 are the same as those shown in the flowchart described inFIG. 2, they are omitted here. As the drive used in the embodiment 2 canhave three write power Pw levels, we set respectively the optimum powerof three types of write patterns obtained in the steps S1105, S1108 andS1111, and we could use them in actual recording. However, as we use adrive that can set only two Pw levels here, we cannot allocate theoptimum power level on all the three types of write patterns. Therefore,in the step S1112, we sought the mean power Pw(y) of the optimum writepower for three types of write patterns, and in the step S1113 we judgedthe write pattern A which will be the farthest value from Pw(y) amongthe optimum write powers of the three types of write patterns Pw(3LT)=57.7 mW, Pw((3L−1)T)=54.0 mW, and Pw((3L−2)T)=56.3 mW. In thepresent embodiment Pw(y)=56.0 mW, and the difference between the writepower of each write pattern and Pw(y) is 1.7 mW for Pw(3LT), 2.0 mW forPw(3L−1)T), and 0.3 mW for Pw ((3L−2)T) and we found that the writepattern A having the farthest write power is the write patternconsisting of the nT=(3L−1) T marks (step S1113).

Then in the step S1114, we set the write power Pw (A) of the writepattern A at 54.0 mW as the write power Pw((3L−1) T) of the writepattern composed of nT=(3L−1)T marks, and in the step S1115 we recordedby changing power the write pattern B consisting of nT=3LT marks andnT=(3L−2)T marks. As a result, in the step S1116 we obtained 56.7 mW asthe Pw (B) at which the jitter is reduced to the minimum. The jitter atthat time was 6.8 mW. In the step S1117, we set the nT=(3L−1) T marks at54.0 mW as the write power Pw (A), the nt=3LT marks and the nT=(3L−2) Tmarks at 56.7 mW as the write power Pw (B), and recorded the randompatterns. As a result, the jitter stood at 7.2 mW and we could obtain apractically passable recording ability. In the step S1118, a “Yes”judgment was given, and the test writing came to a close.

In the step S1116 (FIG. 14) shown in the present embodiment, wedesignated Pw at which the jitter was reduced to the minimum value forPw (B). However, for the sake of convenience, the mean value of theoptimum powers of two types of write patterns may be used. Furthermore,the same effect can be achieved by using the level jitter applied toPRML. Or, the calculation equations shown by Type 1 through Type 5 shownin the embodiment 7 may be used. Or, a write power Pw (B) at which β ofthe respective minimum mark of nT=3LT marks and that of the minimum markof nT=(3L−2) marks nearly coincide may be set (FIG. 15). In the presentembodiment wherein a modulation method with the minimum mark of 3T andthe maximum mark of 14T is used, in specific terms the minimum mark fornT=3LT marks will be a 3T mark and the minimum mark for nT=(3L−2) Tmarks will be a 4T mark. The selection method of Pw (B) in the stepS1116 may be determined by taking into account the compatibility betweenthe medium used and the drive.

While FIG. 14 showed the method of seeking the write power Pw from thewrite power P0 at which the modulation gets 0, FIG. 27 shows an exampleof test writing in case where the write power at which β getsapproximately 10% is set as Pw. For the test-write patterns used in thesteps S1703, S1705 and S1707 of FIG. 27, we used three types of writepatterns consisting of a write pattern formed by nT=3LT marks, a writepattern formed by nT=(3L−2) T marks and a write pattern formed bynT=(3L−1) T. However, the present invention is not limited to thesetest-write patterns. For example, test-write patterns consisting of theshortest mark of each write pattern and the common mark length of eachwrite pattern shown, for example, in the embodiment 6, specifically, inthe step S1703, a write pattern composed of 3T marks being the shortestmark, 11T marks being the common mark, and spaces of a length rangingfrom 3T to 11T, in the step 1705, 4T marks being the shortest mark and11T marks being the common mark, and write patterns composed of 3T-11Tlength spaces, and in the step S1707 a write pattern composed of 5Tmarks being the shortest mark, 11T marks being the common mark, andspaces of a length ranging from 3T to 11T may be used. And in FIG. 27,the write power with β accounting for 10% is used as Pw for each writepattern. However, the optimum value of β may vary depending on themedium or the drive. It is preferable to set the value of β according tothe type of the medium or the characteristics of the drive.

Embodiment 9

For the present embodiment, we will describe a device used for testwriting or actual recording conducted in the above embodiment. Here, asan example of device, we will show an example of the device for 2Tstrategy such as the one shown in the embodiment 1. The overall view ofthe device is shown in FIGS. 16, 17 and 18. Recording data are convertedinto a recording code language by an encoding circuit, are composed by asynchronizing circuit with synchronizing signals generated by asynchronizing signal generating circuit and a composing circuit areinputted into a pulse conversion circuit. Then, they are converted intopulse data by a pulse conversion circuit, shaped into pulse shape by awrite pulse shaping circuit and drive the light source. Up to thispoint, FIGS. 16, 17 and 18 are common.

A device provided with an even/odd classified test-write patterngenerating circuit having two write power levels for classifying evennumber length marks and odd number length marks and for generating writepattern is shown in FIG. 16. An even/odd classified test-write patterngenerating circuit generates respectively write patterns for testwriting composed of even number length marks and write patterns for testwriting composed of odd number length marks and record them on a disk.The recorded signals are detected by a waveform detector, theirrecording ability is evaluated by the reproducing circuit, and therelationship between the recording conditions and the recording abilityis stored in the readout characteristics memory means. Then, a writepower adjusting circuit determines the following write power, andreturns to the write pulse shaping circuit. Incidentally, the even/oddclassified test-write pattern generating circuit described in FIG. 16may be a test-write pattern generating circuit wherein natural number nxlength marks in the window width are classified according to the excessobtained by dividing n by an integer constant of two or more. In thisway, the optimum write power for each write pattern is sought, and inactual recording the respective write power is set in each odd numberlength mark and each even number length mark.

FIG. 17 is an illustration showing the configuration (an example) of adevice wherein the set value of the write power level is one in the caseof using the 2T strategy. It is an example of configuration of thedevice in the case where the value of set levels of the write power issmaller than the number of write patterns as in the embodiments 7 and 8.As in FIG. 16, two types of write patterns are respectively generatedand are recorded on the disk, the recorded signals are detected, and thereproducing circuit evaluates their recording ability. After the optimumvalue of two types of write patterns are set, the write powers of thetwo types of write patterns are evaluated by means of a judging equationrecorded in a judging equation memory circuit relating to a judgingcircuit, and when the judgment value of the write power is equal orbelow the predetermined value, the optimum write power is adjusted inthe write power adjusting circuit by means of a calculating equationstored in the write power calculating equation memory circuit. And whenthe judgment value of the write power is equal or larger than thepredetermined value, a write error judgment is displayed and a NG(impossible to write) is displayed. FIG. 17 shows an example of devicehaving a write power setting level for the 2T strategy (two writepatterns). However, a device having a smaller than n number of writepower setting levels for n number of write patterns may also be used.

FIG. 18 is an illustration showing the configuration (an example) of adevice using random signals without dividing the write patterns for testwriting between even number length marks and odd number length marks.The random signals recorded by test writing are detected in a waveformdetector, and then are classified into even number length marks and oddnumber length marks in a even/odd classifying circuit. In FIG. 18, areproducing circuit, a reproduction characteristic memory means and awrite power adjusting circuit respectively dedicated to even numberlength marks and odd number length marks are provided. These circuitscan be easily realized in a circuit, and they can be easily increased totwo or a larger number. In addition, in FIG. 18, we described on aneven/odd classifying circuit and even a classifying circuit classifyingaccording to the excess obtained by dividing n by an integer constant oftwo or more for natural number nx length marks in the window width canbe equally used. A memory circuit of reproduction characteristics canstore modulation, β and other reproduction characteristics.

This invention also includes the following features.

The present invention is a test writing method for setting recordingconditions for recording information on an optical information recordingmedium, wherein

write patterns classified according to the excess obtained by dividingthe mark length in the recording signals train by an integer constant oftwo or a larger number corresponding to a natural nx marks in the windowwidth are created, and

any write pattern A among the write patterns mentioned above is chosen,and the write powers of other write patterns are chosen in such a waythat the latter may have nearly the same value as the modulation mod (A)for the write power Pw (A) of the write pattern A set by thepredetermined method.

The above predetermined method of the present invention is a method ofrecording and reproducing the write pattern A mentioned above bychanging the write power, seeking a write power P0 (A) at which themodulation gets 0 due to the relationship between the modulation and thewrite power, and setting the value obtained by multiplying the above P0(A) by a constant p as the write power Pw (A) of the write pattern.

The present invention is a test writing method for setting recordingconditions for recording information on an optical information recordingmedium, wherein

write patterns classified according to the excess obtained by dividingthe mark length in the recording signals train by an integer constant oftwo or a larger number corresponding to a natural nx marks in the windowwidth are created, and

any freely chosen write pattern A among the write patterns mentionedabove is chosen, the write power Pw (A) of the write pattern A is set bythe predetermined method, the write pattern A is test written by thewrite power Pw (A) and by changing the write power of other writepatterns within a fixed range including Pw (A) and the write powers ofother write patterns are set.

The above fixed range of the test writing method of the presentinvention is a x Pw (A)≦Pw≦b×Pw (A), and 0.8≦a≦1.0, and 1.0≦b≦1.2.

The above predetermined method of the present invention includesrecording and reproducing the write pattern A by changing the writepower, seeking a write power P0 (A) at which the modulation gets 0 fromthe relationship between the modulation and the write power, and settinga value obtained by multiplying P0 (A) by a constant p as the writepower Pw (A) of the write pattern.

The above test writing method of the present invention includescalculating the modulation by the write power Pw (A) of the writepattern A,

calculating the modulation when the write power Pw (A) of the otherwrite patterns is applied,

comparing the modulation by the write power Pw (A) and the modulation ofother write patterns, and

and test writing by changing the range of changing the write power inaccordance with the comparison result.

The present invention is a test writing method for setting recordingconditions for recording information on an optical information recordingmedium, wherein

write patterns classified according to the excess obtained by dividingthe mark length in the recording signals train by an integer constant oftwo or a larger number corresponding to a natural nx marks in the windowwidth are created, and

a write power is sought by test writing by using any write pattern Aamong the write patterns described above, and the write power of otherwrite patterns by multiplying the write power by a constant q or byadding a constant r.

The present invention is a test writing method for setting recordingconditions for recording information on an optical information recordingmedium, wherein

the first write pattern including odd number length minimum marks of anatural number nx length of the window width and the second writepattern including odd number length minimum marks of a natural number nxlength of the window width are created,

the asymmetry or β or γ of odd number length minimum marks and theasymmetry or β or γ of even number length minimum marks are calculatedin such a way these values may be almost equal, and the write power Pw(odd) for recording the first write pattern and the write power Pw(even) for recording the second write pattern are respectively set.

The above test writing method of the present invention includes marks ofthe same mark length for the first write pattern and the second writepattern and the asymmetry or γ or γ is calculated on the marks of thesame mark length.

The present invention is a test writing method for setting recordingconditions for recording information on an optical information recordingmedium, wherein

the mark lengths in the recording signal train are classified as a mnumber (m is a natural number of two or more) of write patternsclassified according to the excess obtained by dividing the same by aninteger constant of two or a larger number corresponding to a naturalnumber nx length mark in the window width, and recording the same byusing a driver having a laser driver whose write power settable levelvalue is smaller than the m number, and

includes the steps of seeking the optimum write power for each of the mnumber of write patterns and of seeking the extent of variation of eachwrite power of the m number of write patterns according to a certainjudging equation,

the step of setting a common optimum power Pw (opt) according to acalculation equation in the case where the extent of variation is lessthan the predetermined value, and

the step of changing pulse width in the case where the extent ofvariation is equal or larger than the predetermined value and in thecase of a pulse width variable driver, and the step of determining awrite error and not allow the information to be recorded in the case ofa drive of invariable pulse width.

The present invention is a test writing method for setting recordingconditions for recording information on an optical information recordingmedium, wherein

write patterns classified according to the excess obtained by dividingthe mark length in the recording signals train by an integer constant oftwo or a larger number corresponding to a natural number nx marks in thewindow width are created, and

the write pattern is respectively recorded and reproduced by changingthe write power, and a write power Pw′ at which the modulation gets a%(provided that 0<a) from the relationship between the modulation and thewrite power is sought, and the value obtained by multiplying the Pw′ bythe constant p′ is set as the write power of each of the write pattern.

The above test writing method of the present invention consists of testwriting by using confirming patterns wherein the classified writepatterns are mixed at the write power set by each of the write patterns,and by fine adjusting the write power of each of the write patterns.

The above test writing method of the present invention is characterizedin that the classified write patterns are write patterns composed ofeven number length marks and write patterns composed of odd numberlength marks.

The above test writing method of the present invention is characterizedin that the classified write patterns are write patterns formed bynT=3LT marks (L represents pulse number and T represents window width),write patterns formed by nT=(3L−2) T marks, and write patterns formed bynT=(3L−1) T marks.

The above test writing method of the present invention is characterizedin that the classified write patterns are write patterns formed bynT=4LT marks (L represents pulse number and T represents window width),write patterns formed by nT=(4L−2) T marks, write patterns formed bynT=(4L−1) T marks and write patterns formed by nT=(4L+1) T.

The information recording device of the present invention includes atest-write pattern recording means for recording the test-write patternsfor determining the write power on the recording medium,

a waveform detector for detecting the recorded test-write patterns,

a reproducing circuit for reproducing the recorded test-write patterns,

a judging circuit for judging the reproducing characteristics of thetest-write patterns,

a circuit for displaying a write error in the case where a NG(impossible to write) judgment is given by the judging circuit, and

a write power adjusting circuit for adjusting the write power based onthe signal emitted by the waveform detector in the case where GOOD (fitto write) judgment is given by the judging circuit, and

the test-write pattern recording means is a means for recording thewrite patterns classified according to the excess obtained by dividingthe mark lengths within the recording signal train by an integerconstant of two or a larger number corresponding to a natural nx lengthmarks in the window width, and

the write power adjusting circuit is for setting a write power for eachof the classified write pattern.

1. A test writing method for setting the recording conditions for recording information on an optical information recording medium, the test writing method comprising: creating write patterns classified according to the excess obtained by dividing the mark lengths within the recording signal train by an integer constant of two or a larger number corresponding to a natural nx length marks in the window width, and recording and reproducing each of said write patterns by changing the write power, seeking respectively a write power P0 at which modulation effectively gets 0 from the relationship between said modulation and write power, and setting the value obtained by multiplying P0 by a constant p as the write power of each of said write patterns, wherein said constant p is within a range of 1.5≦p≦3.0.
 2. The test writing method according to claim 1 wherein test writings are conducted by using confirming patterns wherein said classified write patterns are mixed with a write power set by each of said write patterns, and the write power of each of said write patterns is fine adjusted.
 3. The test writing method according to claim 1 wherein said constant p is within a range of 2.0≦p≦2.8.
 4. The test writing method according to claim 1 wherein said classified write patterns are write patterns formed by even number length marks and write patterns formed by odd number length marks.
 5. The test writing method according to claim 1 wherein said classified write patterns are write patterns formed by the nT=3LT (L represents pulse number and T represents window width) marks, write patterns formed by the nT=(3L−2) T marks, and write patterns formed by the nT=(3L−1) T marks.
 6. The test writing method according to claim 1 wherein said classified write patterns are write patterns formed by the nT=4LT (L represents pulse number and T represents window width) marks, write patterns formed by the nT =(4L−2) T marks, write patterns formed by the nT=(4L−1) T marks and write patterns formed by the nT =(4L+1) T marks. 